Provided are systems and methods for monitoring the oil to water ratio of drilling fluids. More particularly, systems and methods may be provided for a real-time analysis of shifts in the oil to water ratio of a drilling fluid that is being circulated in a wellbore.
During the drilling of a wellbore into a subterranean formation, a drilling fluid, also referred to as a drilling mud, may be continuously circulated from the surface down to the bottom of the wellbore being drilled and back to the surface again. The drilling fluid serves several functions, one of them being to transport wellbore cuttings up to the surface where they are separated from the drilling fluid. Another function of the drilling fluid is to provide hydrostatic pressure on the walls of the drilled wellbore so as to prevent wellbore collapse and the resulting influx of gas or liquid from the formations being drilled. For these and other reasons, it can be important to precisely know the characteristics and chemical composition of the drilling fluid.
Determining the oil to water ratio in a drilling fluid may be essential to an efficient drilling operation. The oil to water ratio allows operators of a drilling operation to determine the fluid rheology, the impact the drilling fluid may have on the formation, the salinity of the drilling fluid, density, filtration characteristics or requirements, etc. For example, a fluid that is too viscous may reduce drilling efficiency; conversely a fluid that is not viscous enough may be leached out to the formation and lost. A correctly formulated and maintained drilling fluid composition may be necessary to maintain the filter cake and to ensure that drill solids, such as drill cuttings, make it to the surface.
Typically, the oil to water ratio has been measured using a technique called a retort. A retort uses a distillation unit to heat and then distill the oil and water in a drilling fluid. The volume fraction of each is then compared to the original known volume used during formulation of the drilling fluid in order to measure the changes to the drilling fluid during use. This process can take an hour or more. Further, it cannot be done in real-time on the actual drilling mud while it is being circulated, as distillation of the entire fluid would be impractical, thus the process requires the use of a sample of small enough volume to be adequately distilled by the distillation unit in a practical amount of time. As such, the retort process is slower to perform and provides measurements that lag relative to the operation. The retort measurements only illustrate the oil to water ratio of the drilling fluid when the sample was taken and cannot illustrate the oil to water ratio of the drilling fluid as it is presently being circulated. This in turn may lead to delayed correction of the drilling fluid and a reduction in the overall efficiency of the operation.